1. Field of the Invention
The present invention relates to medicine, particularly to laser fiber-optic probes for soft tissue surgery, e.g., for angioplasty or endometriosis.
2. Description of Prior Art
At the present time laser techniques find increasing medical applications, in particular in laser surgery on soft tissue, such as laser angioplasty, endometriosis, or tubular reconstructive surgery. For surgical operations, a laser beam should be delivered to the operation site and converted into other forms of energy, such as heat or acoustic energy, which is concentrated within a specific volume. However, operation sites usually are remotely located with respect to the laser-energy source and are often poorly accessible, especially when the operation must be performed inside a blood vessel to remove a plaque which is a localized area of arteriosclerosis. Plastic surgery of diseased blood vessels is called angioplasty. In laser angioplasty an optical fiber is inserted into a blood vessel, moved along the vessel, and used, e.g., for removing plaque from the inner walls of the vessel.
At the present time, however, optical fiber laser angioplasty can be carried out only in relatively short and straight vessels because existing techniques suitable for such operations allow the beam to exit only in a linear path.
In addition, when plaque areas are located asymmetrically, i.e., not opposite to each other on the inner wall of the vessel, simultaneously with the removal of a plaque area, the linearly-directed beam will damage the opposite inner wall.
Thus, in laser angioplasty the laser beam's energy is used inefficiently because the object being treated is located on the wall of a blood vessel while the beam is directed along the vessel. Also the optical fiber is located in a narrow blood vessel and therefore cannot be curved. This is because, in a curved configuration, an optical fiber may preserve its operation characteristics only when the radius of curvature exceeds 3-10. However, the limited space inside the blood vessel does not allow to satisfy this requirement.
Moreover, in a human body none of the blood vessels are ideally straight and some of them have intricate paths, forming V- or U-shaped configurations. In order to treat hard-to-reach areas in such vessels, the laser beam should be able to operate throughout a wide range of angles. The same is true, not only for angioplasty, but also for other types of laser surgery. A more detailed description of optical-fiber laser-surgery techniques is given in "Optical Fibers in Medicine" (SPIE [Society of Photographic Instrumentation Engineers]1990), Volume MS 11, Bellingham, Wash., U.S.A.
In order to solve the above problem, the applicants of the present patent application have developed a surgical-laser endoscopic focusing guide for a laser-fiber optical link. The device comprises a disposable unit which is connected to the end of an optical fiber link. The unit consists of an endoscopic tube, the front end of which contains an optical head with a mirror lens for directing a laser beam emitted from the unit onto the operation site. The lens bends the beam in a lateral direction onto a tissue to be treated. In an embodiment for laser angioplasty, the unit has a firm attachment directly to a buffer layer of the optical fiber link. This ensures flexibility required for operation in narrow and curved vessels and provides firm attachment of the mirror lens to the tube.
However, the optical head used in the above-mentioned device must have a diameter of at least 2-3 mm and a length of at least 4 to 5 mm. Therefore the use of such a device is limited only to angioplasty of large coronary blood vessels, since the optical head cannot be inserted and guided through blood vessels of a small diameter. Furthermore, the surgical endoscopic optical guide has a very limited area of focusing of a laser beam and therefore a nonuniform distribution of laser radiation over the treated surface, which is dangerous for treating narrow blood vessels with extremely thin walls. A mechanism for the attachment of the optical head to an optical fiber link is sufficiently complicated in structure and expensive to manufacture.